Commit c04167ce authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller

ebpf: add helper for obtaining current processor id

This patch adds the possibility to obtain raw_smp_processor_id() in
eBPF. Currently, this is only possible in classic BPF where commit
da2033c2 ("filter: add SKF_AD_RXHASH and SKF_AD_CPU") has added
facilities for this.

Perhaps most importantly, this would also allow us to track per CPU
statistics with eBPF maps, or to implement a poor-man's per CPU data
structure through eBPF maps.

Example function proto-type looks like:

  u32 (*smp_processor_id)(void) = (void *)BPF_FUNC_get_smp_processor_id;
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 03e69b50
......@@ -155,5 +155,6 @@ extern const struct bpf_func_proto bpf_map_update_elem_proto;
extern const struct bpf_func_proto bpf_map_delete_elem_proto;
extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
#endif /* _LINUX_BPF_H */
......@@ -166,6 +166,7 @@ enum bpf_func_id {
BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */
BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
BPF_FUNC_get_prandom_u32, /* u32 prandom_u32(void) */
BPF_FUNC_get_smp_processor_id, /* u32 raw_smp_processor_id(void) */
__BPF_FUNC_MAX_ID,
};
......
......@@ -662,6 +662,7 @@ const struct bpf_func_proto bpf_map_update_elem_proto __weak;
const struct bpf_func_proto bpf_map_delete_elem_proto __weak;
const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
/* To execute LD_ABS/LD_IND instructions __bpf_prog_run() may call
* skb_copy_bits(), so provide a weak definition of it for NET-less config.
......
......@@ -12,6 +12,7 @@
#include <linux/bpf.h>
#include <linux/rcupdate.h>
#include <linux/random.h>
#include <linux/smp.h>
/* If kernel subsystem is allowing eBPF programs to call this function,
* inside its own verifier_ops->get_func_proto() callback it should return
......@@ -99,3 +100,14 @@ const struct bpf_func_proto bpf_get_prandom_u32_proto = {
.gpl_only = false,
.ret_type = RET_INTEGER,
};
static u64 bpf_get_smp_processor_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
{
return raw_smp_processor_id();
}
const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
.func = bpf_get_smp_processor_id,
.gpl_only = false,
.ret_type = RET_INTEGER,
};
......@@ -1141,6 +1141,8 @@ sk_filter_func_proto(enum bpf_func_id func_id)
return &bpf_map_delete_elem_proto;
case BPF_FUNC_get_prandom_u32:
return &bpf_get_prandom_u32_proto;
case BPF_FUNC_get_smp_processor_id:
return &bpf_get_smp_processor_id_proto;
default:
return NULL;
}
......
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